1. Field of the Invention
The present invention relates to a portable radiation imaging apparatus and a portable radiation imaging system.
2. Description Related to the Prior Art
In a medical field, radiation imaging systems which utilize radiation (for example, X-rays) are known. The X-ray imaging system comprises an X-ray generating apparatus and an X-ray imaging apparatus. The X-ray generating apparatus generates X-rays. The X-ray imaging apparatus detects the X-rays that passed through the subject (patient) and thereby captures an X-ray image of the subject. The X-ray generating apparatus has an X-ray source, a source control device, and an exposure switch. The X-ray source emits the X-rays to the subject. The source control device controls the X-ray source. The exposure switch inputs a command for operating the X-ray source to the source control device. The X-ray imaging apparatus has an X-ray image detection device and a console. The console issues operation commands to the X-ray image detection device, displays an X-ray image, and the like.
The X-ray image detection device has a sensor panel, which is also referred to as a flat panel detector (FPD). The sensor panel converts the X-rays that passed through the subject into an electric signal and thereby detects an X-ray image. The X-ray image detection device immediately transmits the detected X-ray image to the console to display the X-ray image thereon. In comparison with a conventional X-ray image recording device such as an X-ray film or an IP (imaging plate) cassette, the X-ray image detection device offers a user an advantage of viewing the image immediately after the image capture.
There are stationary X-ray image detection devices and portable X-ray image detection devices. The stationary X-ray image detection device is disposed in an imaging room. The portable X-ray image detection device (referred to as an electronic cassette) comprises a sensor panel and a portable housing which accommodates the sensor panel. The electronic cassette is used in combination with a portable console to constitute a portable X-ray imaging apparatus. In the imaging room, the electronic cassette may be attached to a stationary imaging support on which a subject (patient) in a standing position or lying position is imaged. The electronic cassette is also used for portable or bedside imaging, which is X-ray imaging performed in a hospital room of a patient who is incapable of coming to the imaging room, during a ward round.
There are also portable types of X-ray generating apparatuses. One type of the portable X-ray generating apparatuses is a movable X-ray generating apparatus with a movable cart on which the X-ray generating apparatus is mounted. The movable X-ray generating apparatus may be referred to as the mobile radiography unit. The portable X-ray imaging apparatus is mounted on the mobile radiography unit and moved to make the rounds at the hospital rooms, to perform portable imaging (for example, see Japanese Patent Laid-Open Publication Nos. 2002-125960 and 2006-095212).
The X-ray imaging is performed based on an imaging order, that is, information of a request for radiation imaging issued from a medical department such as internal medicine or surgery. The imaging order contains patient information (e.g. the name and the patient ID of a patient), the body part to be imaged, the purpose of imaging, and the like. A radiologic technologist performs the radiation imaging based on the imaging order. The imaging order is managed by a RIS (Radiology Information System) server. The portable X-ray imaging apparatus accesses the RIS server through a terminal such as a console and thereby obtains the imaging order.
The portable X-ray imaging apparatus disclosed in the Japanese Patent Laid-Open Publication Nos. 2002-125960 and 2006-095212 has a wireless terminal with a wireless communication function. The portable X-ray imaging apparatus uses the wireless terminal to access the RIS server through a LAN (Local Area Network) and thereby obtains the imaging order. The LAN is provided with access points, which are wireless relay stations allowing the wireless terminal to connect to the LAN. The access points are provided at important locations in a ward in which the portable imaging is performed, allowing the wireless terminal to obtain the imaging order during the ward round through the hospital rooms.
The access point constantly transmits radio waves called a beacon signal to notify the wireless terminal of its presence. The wireless terminal receives the beacon signal and thereby identifies the presence of the access point, and connects itself to the identified access point. The wireless terminal maintains the connection to the access point, which transmits the beacon signal, as long as the wireless terminal receives the beacon signal. The wireless terminal is disconnected from the access point when the wireless terminal is out of a range (coverage) of the beacon signal. Naturally, in a case where there are two or more access points, the communication quality is stable when the connection to the access point with higher field intensity than the others is established. A technique to compare the field intensities of the access points and automatically switch the connection to the access point with high field intensity is known (for example, see U.S. Patent Application Publication No. 2010/0169423 corresponding to WO 2009/031411).
The U.S. Patent Application Publication No. 2010/0169423 discloses an electronic cassette having a wireless communication function. In a case where the electronic cassette is moved through imaging rooms, the electronic cassette compares the field intensities of the access points, and switches its connection automatically to the access point with high field intensity (paragraph 0072).
The technique for automatically switching the connection to the access point with high field intensity as disclosed in the U.S. Patent Publication Application No. 2010/0169423 is referred to as roaming. As described above, the ward round is made to perform the portable imaging with the use of the mobile radiography unit, on which the portable X-ray imaging apparatus is mounted. Well-functioning roaming is convenient for constantly ensuring the stable communication quality.
At the start of the portable imaging, first, the console is operated to access the RIS server and obtain imaging order(s) in a cart parking area, in which the mobile radiography unit is parked. After the imaging order is obtained, the portable X-ray imaging apparatus is mounted on the mobile radiography unit. The radiologic technologist with the mobile radiography unit is headed for the ward and makes the ward round through the hospital rooms. An additional imaging order may occur during the ward round. By accessing the RIS server, the additional imaging order is obtained in the ward. Failure in receiving the additional imaging order requires the radiologic technologist to return to the hospital room of the patient who has finished radiation imaging, and perform re-imaging of the patient.
To avoid such trouble, inventors have examined the provision of a function to transmit a delivery request for the imaging order by accessing the RIS server through an access point and a roaming function, to the console having the wireless communication function. Transmitting the delivery request for the imaging order at regular time intervals prevents the failure in receiving the additional imaging order even if the additional imaging order occurs during the ward round. The roaming function automatically switches the connection to the access point with high field intensity. Thus, the communication quality becomes stable, preventing the reception error of the imaging order.
However, experiments revealed that the sole provision of the roaming function as disclosed in the U.S. Patent Application Publication No. 2010/0169423 cannot prevent roaming problems such as failure in switching the connection to an appropriate access point. For example, in a case where the mobile radiography unit is moved from a first floor to a second floor of a ward, the console is connected to an access point on the first floor with high field intensity while the mobile radiography unit is on the first floor. When the radiography unit with the console is moved to the second floor, the field intensity of an access point on the second floor is higher than that of the access point on the first floor. If the roaming works properly, the console switches its connection to the access point with high field intensity on the second floor. However, in actual cases, the console often maintains its connection to the access point on the first floor and does not switch its connection to the access point on the second floor in a case where the radio waves from the access point on the first floor reach the second floor.
The inventors considered one of the reasons for the roaming problems as follows. The roaming function as disclosed in the U.S. Patent Application Publication No. 2010/0169423 detects the field intensities of the access points and compares the detected field intensities with each other while the mobile radiography unit is on the move. In this case, the field intensities vary with the move of the mobile radiography unit, so that the detection may not be accurate. Once the detection of a change in the field intensity is failed, a cue for switching the connection to the appropriate access point is lost. This causes the roaming problem, namely, the connection to the currently-connected access point is maintained despite the presence of another appropriate access point. There is another factor for causing the roaming problems. Recently, mobile wireless terminals have been rapidly prevailing in medical facilities. Although accurate measurement of the field intensity is indispensable for appropriate roaming, it is becoming more difficult due to interference from the increasing wireless terminals.
The failure (reception error) in receiving a new or additional imaging order for the portable imaging during the ward round increases burdens on the radiologic technologist, so that they strongly demand countermeasures to avoid the reception error. According to a survey conducted by the inventors, there are about 20 imaging orders plus up to 30 or more emergency imaging orders for the portable imaging per day. The portable imaging is normally performed by one radiologic technologist. The radiologic technologist may perform the portable imaging of up to 50 or more images in one day. A single imaging procedure may take approximately 5 minutes. However, the patient who is the subject of the portable imaging often has difficulty in moving his/her body, so that positioning, such as raising the upper part of the body of the patient and placing the electronic cassette at an appropriate position, takes a long time. The failure in receiving the additional imaging order increases the burdens on the radiologic technologist because he/she needs to return to the hospital room which he/she has left and do the positioning or the like all over again.
The Japanese Patent Laid-Open Publication Nos. 2002-125960 and 2006-095212 and the U.S. Patent Publication Application No. 2010/0169423 do not point out explicitly or suggest the above-described problems and their solutions. The U.S. Patent Application Publication No. 2010/0169423 discloses that the electronic cassette performs roaming based on the field intensity. However, it only discloses the general art of roaming and does not clearly disclose configuration and procedure of the roaming.